Amebic Liver Abscess: Epidemiology
Amebic liver abscess (ALA) is a serious, but readily treatable form of hepatic infection. In order to understand the clinical features of this condition in the United States, we reviewed the medical histories of 56 patients with ALA at two large San Francisco Hospitals from 1979 to 1994. Patients were divided into the following groups based on the presumed manner in which they had acquired ALA: those born or raised in the United States, with a history of travel to an endemic area (Tr-ALA); those from an endemic area, but living in the United States for less than one year (En-ALA); and those neither from nor having traveled to an endemic area (N-ALA). We found distinct clinical patterns in patients from different epidemiological groups. Patients with Tr-ALA were a decade older than those from endemic regions, were more likely to be male, and tended to have an insidious onset. Furthermore, compared to patients with En-ALA, those with Tr-ALA were more likely to have hepatomegaly (P < 0.0001) and large abscesses (ALA >10 cm; P< 0.01). One third of the patients studied had no associated travel history or endemic origin as risk factors. Of these, 63% had a condition consistent with severe immunosuppression, such as infection with the human immunodeficiency virus (HIV)/ malnourishment with severe hypoalbuminemia, or chronic infection. In patients with N-ALA, the presence of a presumed immunosuppressed state increased significantly, as compared to patients with endemic or travel risk factors for ALA. During the last five years of the study, one third of all patients diagnosed with ALA were HIV positive (including 2 with a new diagnosis of AIDS), many of whom were discovered to be HIV-infected only after presentation with ALA. We conclude that travel to and origin in an endemic area are important risk factors for the development of ALA, and patients in these different epidemiological groups appear to have distinct clinical features. Further, in the absence of recognized risk factors, the development of ALA may suggest an immunocompromised host.
Infection with the parasite Entamoeba histolytica is common worldwide. Most patients infected with Entamoeba histolytica have only colonic symptoms and signs. Although less common than colonic amebiasis, extra-intestinal amebiasis is often more consequential. The most frequent form of extra-intestinal amebiasis is amebic liver abscess (ALA), which may develop serious complications if not rapidly detected and properly managed. With appropriate management, however, patients with ALA have an excellent prognosis.
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Although Entamoeba histolytica infection is most common in underdeveloped countries, immigration and the modernization of transport have contributed to an increased incidence and awareness of ALA in developed countries, such as the United States. Therefore, the aim of this study was to investigate the clinical features of patients with ALA in the United States. We report on a large cohort of patients with ALA and address both the epidemiologic profiles and clinical characteristics of patients with ALA in this setting.
Methods
Amebic liver abscess was identified in 56 patients between January 1,1979, and December 31,1994, at two hospitals affiliated with the University of California, San Francisco, Moffit-Long Hospital and San Francisco General. Each ALA was confirmed by radiological or surgical demonstration of an intrahepatic abscess cavity and by positive amebic serology. A presumptive diagnosis of ALA was made in two patients; amebic serology was not performed, but each had amebic stool cysts and a rapid clinical response to antiamebic treatment. In one patient, a histopathologic diagnosis of disseminated amebiasis was made at autopsy. Specimens for parasitology were collected from fresh stools or drainage from interventional radiology or surgery. Patients with non-amebic etiologies for liver abscesses were excluded. Substantial alcohol consumption was considered to be present when ingested ethanol was >150 grams/d. A state of clinical immunosuppression was defined by the presence of either of the two following conditions: severe clinical malnutrition with muscle wasting and an albumin level of less than 2.6 gram/dl, demonstrated by physical and laboratory examination and having no other potential cause; or a serious, chronic, underlying infection, such as tuberculosis or HIV infection. Recurrence was defined as an ALA appearing subsequent to initial clinical or radiographic resolution.
We defined the following epidemiologic profiles: Endemic ALA (En-ALA) occurred in patients born and living the majority of their lives in an endemic region, who had been in the United States for less than one year. In this study, 16 patients came from Mexico, 7 from Asia, and 4 from South America. ALA occurring after travel (Tr-ALA) occurred in patients born or having lived the majority of their lives in the United States, who had a reported history of travel to a country where amebiasis is endemic. In this study, eight had travelled to Mexico, four to Asia, and one to South America. The final epidemiologic group was considered to be those neither from nor having traveled to an endemic area (N-ALA). Acute and chronic ALA were defined by the presence of symptoms for less than or more than 14 days, respectively. Statistical analyses were performed with either Fisher’s exact test or the Student’s / test. This study was approved by the Committee on Human Research of the University of California, San Francisco and was performed in accordance with the guidelines set forth in the Declaration of Helsinki for ethical conduct in the study of human subjects. buy cialis professional